Spark plug construction



I I I N H R F EICHTER SPARK PLUG CONSTRUCTION Aug. 9, 1949.

Filed Oct. l, 1947 Aug. 9, 1949.

Filed Oct. 1, 1947 H. R. FEICHTER SPARK PLUG CONSTRUCTION 4 Sheets-Sheet 2 Harold B. fe'sz'c lzer At tornegs Aug. 9, 1949. H. R. FElCHTER SPARK PL UG CONSTRUCTION 4 Sheets-Sheet 5 Filed Oct. l. 1947 grun/Mo&

Harold H. Fe i c/z 'er W 7% Atiornegs Aug. 9, 1949. H. R. FEICHTER SPARK PLUG CONSTRUCTION 4 Sheets-Sheet 4 Filed Oct. l, 1947 w u T r W m.

u I /N w II Attornegs Patenta! Aug. 9,1949

2378359 SPARK PLUG CONSTBUCTION Harold'lt. Feichter, Canton, Ohio, sior to United States Quar'y Tile Company, Carlton. z Ohio, a corporation of Delaware Application October 1, 1947, Serial No. "7,350

8 Claims.

The invention relates to spark plug construction and to spark plugs for use in internal combustion engines for automobiles, aircraft, or wherever it is desired to ignite a combustible mixture.

In a usual spark plug there are included a. multplicity of parts some of which are metal and which require a relatively large number of manufacturing Operations for the production of the separate parts and their assembly.

In a usual spark plug there is included a metal ground shell in which a tubular insulator is inserted, and the tubular insulator has a bore extending entirely through the insulator, and a rod electrode is located in and extends through the bore of the insulator.

At the lower end of the metal ground shell there is welded or otherwise secured a ground electrode, and the lower end of the central rod electrode is spaced from the ground electrode. It is necessary to provide a gas scaling cement between the rod electrode and the bore of the insulator and it is also necessary to provide a gas tight seal between the insulator and the shell.

In other words a usual spark plug includes a multiplicity of parts which make the cost of production relatively expensive, the assembly of the parts being complicated and difficult to control to provide for a uniform finished product which does not deteriorate in use.

The objects of the present invention include the provision of an improved spark plug construction which is inherently adapted for a long period of use and which requires less metal than a usual spark plug Construction, metal having become scarce as compared with ceramic material, and in which there is a reduction in the number of parts required to produce the improved spark plug on the one hand, and which provides the spark plug with substantially improved properties as compared with present spark plugs onthe other hand. One of the more important of these improved properties is the minimizin of the necessity of replacing the spark plug at intervals as 'frequently es has been necessary prior to the present improvements.

.The properties of the improved spariplugs of the present invention include freedom from gas leakage, freedom from rapid deterioration of the electrodes of the spark plug, convenient replaceability of the ground electrode, an arrangement of the reduced number of parts permitting broad scope in the design as'to the size and shape of the parts of the spark plug, a relative arrangement of the size and shape of the parts of the spark plug whereby there may be a greatly increased length of the electrical leakage path between the central electrode of the plug and ground, without increasing the overall length of the plug as compared with conventional practice. A further property of one form of the improved spark plug of the present invention in addition to the foregoing is the maintaining of a constant position of the lower end of the central electrode, and the transfer of heat by convection through circulation of a conducting liquid as well as by its own conduction, from the tip of the insulator or e1ec-` trode to other portions and surfaces of the insulator.

The foregoing and other objects are attained by the spark plug construction, parts, combinations, and sub-combinations, which comprise the present invention, the nature of which is set forth in the following general statement. and preferred embodiments of which together with their mode of use are set forth by way of example in the following description, and which are e particularly and distinctly pointed out and set forth in the appended claims forming part hereof;

The nature of one preferred embodiment of the improved spark plug of the present invention may be stated in general terms as including an insulator body preferably of fired ceramic material, the insulator body having formed therein a well with an open upper end and the insulator body including a bottom wall extending across the lower end of the well. Electrode material is located in the well, and the insulator body includes a lower end having formed thereon external threads adapted for being screwed into an internally threaded opening in the wall* of a combustion chamber such as the combustion chamber of an internal combustion engine. A replaceable metal ground electrode is provided on the lower end of the insulator body adjacent the bottom wall of the well.

By way of example, a number of embodiments of the improved spark plug construction of the present invention are illustrated in the accompanying drawings forming part hereof, in which Figure 1 is a. longitudinal axial sectional view of a first preferred embodiment oi' improved spark plug hereof;

Fig. la is a similar view of the insulator body shown in Fig 1, before assembly in the complete spark plug;

Fig. 2 is a similar view of a second embodlnent of the improved spark plug construction hereof;

garancia Flg. 3 is a similar view oi a third t r o! the improved spark plug construction hereof:

Fig. 4 is a similar view of a four-th embodiment "mi the improved spark plug construction hereoi;

Flg. is a view similar to Fig. 1 oi a sixth embodlment of the improved spark plug construction hereoi Fig. 11 is a view similar to Fig. 1 of a Seventh embodiment oi' the improved spark plug construction hereof.

Fig. 12 is a bottom *plan view of the spark plug construction of Fig. 10 looking in the direction of the arrows |2-| 2, Fig. 10;

Flg. 13 is a transverse cross section of the spark plug construction of Fig. 10 as on the line i3-i3, Fi 10;

Fig. 14 is a view similar to Fig. 1 of an eighth embodiment of the improved spark plug construction hereof;

Fig. 15 is a similar view of a ninth embodiment oi the improved spark plug construction hereoi; and

Flg. 16 is a similar view of a tenth embodiment of the improved spark plug construction hereof.

Similar numerals refer to similar parts throughout the several views.

The first preierred embodiment of the' improved spark plug herecf is illustrated in Fig. 1

and is indicated generaliy by lil and includes an insulator body ll preieraby made' of fired ceramic material, preferably having a high alumina content of upwards oi 92 per cent, and also other ingredients, such as set iorth in any of my U. S. Letters Patents No. 2,413,441, No. 2,414,367, No. 2,414,368, and No: 2,414,369.

The insulator body il is shown in Fig. 1a before assembly in the complete spark plug o, and the insulator body Il has formed therein a well |2 with an open upper end !3, and the insulator body ll furthermore includes a bottom wall |4 extending across the lower end of the well !2. The insulator body Il is elongated, and the well l2 extends longitudinally coaxially with the longitudinal axis IS ot the insulator body ll. Metal electrode material is located in the well !2 which may be as shown in Fig. 1 a rod IS of metal such as steel. The upper end ll of the well |2 may be enlarged and provided with internal threads, and the metal electrode rod !6 may have an enlarged head s which is externally threaded and screwed in the internally threaded enlarged upper end l'l of the well l2. The bottom wall M is preferably thinner than the surrounding walls ot the insulator body, and in itself seals the lower end of the well l2, and covers the lower end of the electrode rod IS therein. The bottom wall M preferaby has 'a thickness between the limits oi '5 thousandths and 125 thousandths of an inch.

In addition, when deslrable, the electrode rod IS may be sealed in the well |2 in a usual manner as by ce-amie cement.

The insulator body li has a reduced lower end indicated generally by s which includes an intermediate externally threaded portion 20 and 'a still smaller externally threaded extremity 2I.

The spark plug o iurthermore includes a replaceable ground electrode indicated generally by i e hard metallic substanca, and which includes an internally and externally threaded errule por tion 23 whose internal threads are screwed on the externally threaded extremity 25 oi the insulator body M, and the external threads of the fer-rule 23 match the externally threaded portion 20 of the insulator body H, The replaceable ground electrode 22 furthermore includes one or more electrode tips or points 24 made of nickel or like material and extending inwardly from the ferrule portion 23. The insulator body li furthermore includes a larger upper portion 25 and an annular shoulder 28 between the inner end of the threaded portion 20 and the larger upper portions 25, which has a larger transverse cross section than the transverse cross section at any place oi the reduced lower end !9.

A metal combustion chamber wall 27 which may be a wall oi a combustion chamber of an internal combustion engine has formed therein an internally threaded opening 28 in which are screwed the externally threaded lower end portion 20 of the insulator body H and the externally threaded ferrule portion 23 of the replaceable ground electrode 22.

In using the spark plug lil the central rod electrode- !6 and the grounding metal combustion chamber wall 21 are connectedin a usual ignition circuit which applies a potential to the central electrode rod !6, and from the lower end thereof contacting the well bottom wall M potential is applied to the bottom wall id until its charge is suihcient to cause a spark between the bottom wall !4 and the electrode tips 24.

In the improved spark plug in the upper portion 25 of the insulator body li may have any desired form and dimensions which are not subject to the form and dimensional limitations of a usual spark plug where the ground shell must be crimped over or otherwise fastened to an enlargement on the usual insulator body.

In the improved spark plug o there is freedom from gas leakage by reason of the location of the central electrode !6 in the well !2, the solid bottom wall !4 of insulating material extending across the lower end of the well !2. Thua protecting th central electrode IS prevents rapid deterioration of the lower end of the electrode IS. When the electrode tips of the ground electrode 22 become burnt oti too much, a replacement ground electrode 22 may be conveniently A andeasily applied to the insulator body ll. It is also to be noted that the length of the upper portion 25 of the insulator body H is substantial whereby there is a greatly increased length of the electrical leakage path between the upper head s of the central electrode IE and the grounding combustion chamber wall 21, this increased length of the electrical leakage path being effected without increasing the overall length of the plug as compared with conventional practice in spark plug construction where ground shells are used which extend a considerable distance above the combustion chamber wall in which the spark plug is mounted.

In Fig. 2 there is shown a second embodiment of the improved spark plug hereof indicated generally by iill and which is generally similar to the spark plug o, but in the spark plug no the insulator body Hi has a bore z extending entirely through the body, and a center electrode I Is located in the bore |l2 has its lower end protruding below the lower end of the insulator body ill. In the spark plug o there is also a :2 which is made oi metal such as steel or other 76 rep aro electrode The p rk plug 110 has all the advantages o! the spa-k plug with the exception of lacking a central electrode in a well.

In Fig. 3 there is shown a generally conventional spark plug ndicated generally by 219 including a ground shell 230 at the lower end of which there is screw connected a replaceable ground electrode 222 which constitutes one o! the improvements of the present invention. The ground shell 230 has mounted therein in a usual manner an insulator 211 in the central bore 212 of which there is sealed a central electrode 219 in the usual manner.

In Fig. 4 there is shown a spark plug indicated generally by 310 which is o! generally conventional construction including a ground shell 230 mounting an insulator body 311 which is modifled rrom conventional construction by including a well 312 having a bottom wall 314 extendlng across the lower end of the well 312, this being one of the improvements of the present invention. There is located in the well 912 a central electrode 316.

In Fig. 5 there is shown a. spark plug indicated generally by no which is of modified conventional construction and includes a ground shell 430. one of the improved removable ground electrodes of the present invention indicated generally by 422 is screw connected to the lower end of the ground shell, and the ground shell mounts an insulator body 411 which is formed to include another of the improvements of the present invention, namely a central well 412 having a bottom wall !14 extending across its lower end. A central electrode 119 is located in the well 412.

In Fig. 6 there is shown a modified insulator body indicated generally by 911 which is generally similar to the insulator body 11, the insulator body 511 having formed therein a central well 512 having an open upper end 919 and a bottom wall 514 extendlng across the lower end o! the well 512. `Diirering from the solid bottom wall 14 of the insulator body 11, the bottom wall 514 has a microscoplc hole 514-1 formed therethrough by being punctured by a high tension electrical discharge passed therethrough by placing the wall 519 between electrodes of an electric circuit in which there is a sumcient potential diiference between the electrodes to effect the puncturing. In Fig. 6, the microscopic hole 514--1 is necessarily magnifled.

For properly locating the hole 514-1, the top face of the bottom wall 514 slopes to a central point 514-2 which insures that the punctn'ing high tension electrical discharge will pass through the wall 514 at the central point ill-2, the wall 514 being thinnest at' that point.

In Fig. '7 there is shown another modified in'- sulator body indicated generally by 911 which is also generally similar to the insulator body 11, the insulator body 911 having formed therein a central well 612 having an open upper end 919 and a bottom wall 014 extending across the lower end of the well 912. The bottom wall 14 oi' the insulator body 11 is formed entirely of insulation material, preferably fired ceramic. material. The bottom wall 614 diifers from this in that the bottom wall 914 has one or more fine metallic wires such as platinum extending therethrough, these wires being inserted in the bottom wall before the flring is eflected, the flring senin: seal the wires in the bottom wall. r

In Flg. 8 there is shown a modified insulatobody indicated generally by '111 which is again generally similar to the insulator body 11, the

insulator body '111 having orned therein a central wellllz having an open upper end 113 and a bottom wall '114 extending across the lower end 5 o! the well '112. Instead of being of insulation material as is the solid bottom wall 14 of the insulator 11, the bottom wall 114 includes a portion or is entirely made. as shown in the drawins. of conducting material, such as a combinetion of ceramic material and a metallic powder such as iron. nickel, chromium, or tungsten, sintered together.

The insulator bodies 511, 911, and 111 each includes a different means whereby a reduced potential differenc is required to eflfect the passage of an electrical discharge or current through their respective bottom walls 519, 914, and '114, as compared with the potential difference required to effect the passage oi a discharge through the solid bottom wall 14 of insulation material of the insulator body 11, where all of the bottom walls have the same thickness.

In Fig. 9 there is shown' a spari: plug indicated generally by 910 which is generally similar to the spark plug 10, but in the spark plug 010 the ground electrode 922 is formed by sprayecl metal onvthe reduce'd lower end 919 of the insulator body 911.

'It should also be noted that the replaceable ground electrode 22 on the insulator body 11 as shown and preferably is screw connected with the insulator body 11. In addition to being merely screwed on the insulator body 11, the replaceable ground electrode 22 may be thermally sweated thereon.

In Figs. 10, 12, and 13 there is shown' a spark plug indicated generally by 910 which is generally similar to the spark plug 10 with the exception of the Construction and arrangement of the well and central electrode. The spark plug 910 includes an insulator body 911 having formed therein a central well 912 having an open upper end 919 and a bottom wall 914 extending across the lower end of the well 912. The well 912 has an increased diameter as compared with the diameter of the well 12 of the insulator body 11 of the spark plug 10.

In the lower end of the well 912 there is located a body of conducting liquid preferably liquid metal 918-1 which may be mercury or a lower melting alloy of bismuth, tin, lead', and antimony, or

similar material. There is also located in the well 912 a metal electrode rod 915, the lower end of which extends into the body of liquid metal 919-1, and the metal electrode rod 916 has an enlarged head 919 which is externally threaded and screwed in the internally threaded enlarged upper end 91'1 of the w'ell 912. A body of cement 931 seals the upper portlons of the electrode rod 916 between the body of liquid metal 916-1 and the head 919.

In the spark plug 910 the lower body of liquid metal 916-1 and the electrode rod 916 whose lower end is immersed in the body of liquid metal 919-1 constitute a composite central electrode in which the lower end of the body of liquid metal 918-1 always rests upon the upper face of the well'bttom wall 914. In other words the position of the lower end of the composite central electrode of the spark plug 910 always remains constant, where as disintegration of the lower tip of the central electrode rod 919 may take place i! the lower tip of the central electrode rod 919 extends to the top surface of the well bottom 76 wall 914, and-no body of liquid metal 919-1 is used. The body of liquid metal SIE-l flows into any void produced in it on top of the well bottom wall 9 i 4.

Moreover, in the operation of an internal combustion engine, for example, in which the spark plug so is in use, the hot gases in the combustion chamber served by the spark plug so heats the lower end of the spark plug slfl and the body of liquid metal SIS-l therein causing circulation of the liquid metal SIS-l, whereby there is a transfer of heat from the lower end 919 of the insulator body 9 to upper portions and surfaces of the insulator body 9| Lthis transfer of heat being efiected by convection of the body of circulating liquid metal SIS-l, as well as by its own conduction.

In Fig. 11 there is shown a spark plug indicated generally by no which is generally similar to the spark plug 8 Io and includes an insulator body lflll having formed therein a central well o having an open upper end os, and the insulator body o has a lower end !OIS which has 'formed therein a bore lon-l which hasa diameter reduced from that of the well |0|2. An

intermediate electrode shank uns- 2 is located and sealed in the bore lfllZ-l and has on its upper end an 'enlarged 'head ING-3 which ts and seals the lower end of the bore um. A body of conducting liquid IOIG-l is located in the lower end of the well |0|2 and rests upon the top of the enlarged head 'IMB-3 on the intermediate electrode-shani: lola-2. A metal electrode rod IMB is located in the well oz and has its lower end immersed in the body of conducting liquid IME-I, and a body of cement oa sea'ls the upper portions of the electrode rod |0I6.v p v i In Fg. 14 there is shown a spark plug indicated generally by I o which is generaly similar to the spark plug 910. The spark .plug o includes an insulator body IIII having formed therein a central well I I !2 having an open upper end Ill3 and a bottom wall, ||I4 extending across the lower end of the well 12. The insulator body Illl has areduced lower end ll |9 having 3 a bottom face llle-l, and the well bottom wall IIM is spaced above the bottom face ll |8-|.

In the lower end l l 19 of the insulator body I I I l of which is a layer of 'powdered carbon ING-4.

There is also located in the well Il !2 a metal 'electrode rod IIIB, the lower end of which extends into the layer of powdered carbon IS-4.

In Fig. 15 there is shown a spark plug indicated generally by zo which includes the improvements of the spark plug o embodied in a construction which is otherwise conventional.

In Fig. 16 there is shown a spari: plug indicated generally by mo which is generally similar to the sparl': plug zo, with 'certain exceptions. -The spark plug !310 includes an'insulator body a with a bottom face |3|9-l and the insulator body |3|l has formed therein a' well |3|2 having a bottom wall |3|4 extendlng across the lowr end of the well 1312. The bottom wall III-4 is sp'acd* above the bottom face NIS-I of the insulator body ISH, and in the lower end |3|9 oi' the insulator body ISH' there ple and the scope of the present invention is not limited to the same or to the particular details thereof but is commensurate with any and all novel subject matter contained herein which may at any time properly under the patent laws be set forth in the claims hereof or originating herein, and the elements of an such claims are intended to include their functional or structural equivalents.

I claim:

1. In'spark plug construction, an insulator body, the insulator body having formed therein a well with an open upper end and the insulator body including a bottom wall extending across. the lower end of the well, electrode material in the well, the insulator body including a lower end having formed thereon external threads adapted for being screwed into an internally threaded opening in the wall of a combustion chamber, and a replaceable metal ground electrode on the lower end of the insulator body adjacent the bottom wall of the well.

2. In spark plug construction, a fired ceramic insulator body, the insulator body having formed r therein a well with an open upper end and the insulator body including a bottom wall extending across the lower end of the well, electrode material in the well,'the insulator body including a lower end having formed thereon external threads adapted for being screwed into an internally threaded opening in the wall of a combustion chamber, and a replaceable metal ground electrode on the lower end of the insulator body adjacent the bottom wall of the well.

3. In spari; plug construction, an insulator body, the insulator body having formed therein a well with an open upper end and the insulator body including a bottom wall extend'ng across the lower end of the well, electrode material in the well, the insulator body including a lower end having formed thereon external threads adapted body including a bottom wall extending across the lower end of the well, electrode material in the well, the insulator body including a lower end having formed thereon external threads adapted for being screwed into an internally threaded opening in the wall of a combustion chamber, and a metalground electrode on the lower end of the insulator body adjacent the bottom wall of the well.

5. In spark plug construction, an insulator body, the insulator body having formed therein a well with anopen upper end and the'insulator body including a bottom wall extending across the lower end of the well; electrode material in the well. the insulator body including a lower end having formed thereon external threads adapted` 9 of the insulator body adjacent the bottom wall of the well, the bottom wall of the well having a microscopic hole formed therein by high tension electrical discharge.

G, In spark plug construction, an insulator body, the insulator body having formed therein a well with an open upper end and the insulator body including a bottom wall extending across the lower end of the well, the bottom wall oi the well having a microscopic hole formed therein by high tension electrical discharge. 4

e 7. In spark plug construction, an insulator body, the insulator body having formed therein a well with an open upper end and the insulator body including a bottom wall extending across the lower end of the well, the insulator body including a lower end having formed thereon external threads adapted for being screwed into an internally threaded opening in the wall of a. combustion chamber.

8. In spark plug construction, an insulator body, the insulator body having formed ther-ein a well with an open upper end and the insulator body including a bottom wall extending across the lower end of the well, the insulator body 25 505,()85

including a lower end having !ormed thereon 'external threads adapted for being screwed into REFERENCES CITED The following references are of record in the file of this patent:

15 UNITED STATES PATENTS Number Name Date &42,646 Jefiery Dec. '1, 19, 09 1,205,422 Arnold Nov. 21, 1916 1,247,102 Forbes Nov. 20, 1917 20 1,941,279 Sharpnack Dec. 26, 1933 2,093,848 Randolph u... sept. 21, 1937 FOREIGN PATENTS Number Country Date Great Britain Apr. 28 1939 

